Microphone



Jan. 1, 1935. J. L, SNOEK 1,986,609

MICROPHONE I Filed March 28, 1932 INVENTOR JACOB LOUIS SNOEK ATTORNEY N-:1-1-E' S E PATENT OFFICE This invention MICROPHONE i Jacob Louis Snoek, Eindh'oven, Netherlands, ass'ignor to Radio Corporation of America, a corporation of Delaware Application March 28, 1932, Serial Germany April 24, 1931 (Claims. (Cl. 119-123) relates to a device used" in microphones comprising a plurality of diaphragms. Microphones of this type are possessed of a greater sensitiveness than microphones com- 5 prising a single diaphragm. In most'cases, however, this greater sensitiveness can only partly be profited by diaphragms with example, the sound from one point in space on account of the position of the respect .to each other. If, for waves catch the microphone and the surface of one of the diaphragms is giventhe most favourable position with respect to the other diaphragms will less favourable position,

in the reception of the different shadow effect? frequencies or that. catch the diaphragm able position but not extent 'the other diaphragms.

the sound source then in general occupy a thus producing a the high frequency waves occupying the most favouror at least to a very lower This is due to the fact that in contradistinction. to the low frequency waves the high frequency of their small wave waves in view length cannot flow around the walls of the microphone. Owing to this deformations in the reception occur. It has been supposed hereinbefore that the microphones are furnished with flat will be appreciated that the above reasoning also holds. good for microphones comprising diaphragms of other shape, for example, slightly curved diaphragms.-

diaphragms. However, 'it

For conveniences sake flat diaphragms will be considered hereinafter.

If the microphone is given a position different from that just refe sound source then ception remains to a case the surfaces of rred to with re this deformation in the respect to the greater or lesser extent. In the diaphragms extend in parallel to each other and into the direction of the sound source, then equivalent, it is true,

phragms is the position of the diabut not the most favourable for the reception.

The drawback reduced by resorting in which the sound waves are'lead to the microof the shadow effect might be to the known construction phone through a mouth piece branched into two tubular members debouching in front of the diaphragms. However,

this construction has the drawback that there occur resonance phenomena avoid the funnel-or hornshape of the said phenomena entail at the same some frequencies and congive rise to deformation.

the said shadow effect the to the invention comprises two or more flat or substantially flat surfaces which 1 may be given diflere nt positions and consist of said surfaces being placed point of space, then .and the low frequencies affect the diaphragms as efficiently as possible. In this manner the total sensitiveness of the microphone is increased up to the maximum value without affecting the 5 quality.

If the sound source is concentrated-in a single in case of using a microphone comprising two diaphragms placed on either side of the microphone and in parallel to each other, 20 a suitable form of construction is obtained, for example, if a plate is .pivotally fixed to the circumference of the housing of the microphone in the vicinity of each diaphragm. Of course, the microphone is placed in such a manner that the 25 aperture between the reflecting surfaces and the diaphragms is turned to the sound source. In addition to the desired acoustic effect obtained, this form of construction has the advantage that the plates may be turned inwards in such a manner that they are placedin parallel to the diaphragms, thus protecting the latter against mechanical damaging when the microphone is not used. I

Preferably, the angle between the diaphragms 35 and the plates is 45 whilst the surface of the plates is so chosen that the projections of-the plates on the diaphragms entirely cover the latter in this position.

The invention will be more clearly understood 40 by reference to the accompanying drawing, representing by way of example, one embodiment thereof.

cate with each other through an aperture in the wall 1 (not represented). The chambers are shut oil by the diaphragms 6 and '7 respectively whose rim is clamped between the wall 1 and the ridges 8 and 9 fixed to the wall by means of bolts 10.

At 11 and 12 two plates 13 and 14 are pivotally fixed on one side of the circumference of the wall 1. In the drawing the angle between diaphragms and plates is 45 but may also have another value. Furthermore it is not imperative that the angles have the same value. By the arrows shown in Fig. 1 is indicated that sound waves catching the microphone in the direction 15 are reflected on the membranes in the direction 16. It will be obvious that in this way both low and high frequency waves catching the reflecting surfaces 13 and 14 from the direction 15 will he received as efliciently as possible by the microphone.

I claim:

1. A sound translating device comprising a plurality of diaphragm; in which a, plurality of substantially fiat surfaces which may be given different angular positions are placed in the vicinity of at least one diaphragm, said surfaces consist=- ing of a sound reflecting material.

2. A translating device as claimed in claim 1 for use as a microphone in which two diaphragms are placed in parallel to each other on either side of the microphone and in which a soundreflecting plate is pivotally fixedto the outer edge of the housing of the microphone in the vicinity of each diaphragm.

."a. A device as claimed in claim 1, in which the angle between diaphragm and plates is substantially 45 and in which the surface of the plates is such that the projection of the plates on the diaphragms covers the surface of the diaphragms.

4. A sound transition device comprising a rectangular wall of insulating material forming a chamber to retain carbon granulars, a plurality of diaphragm mounted on each side of said wall,

and a plurality of adjustable plates having surfaces of sound reflecting material pivotally fixed to one side of the circumference of said wall so as to open in a book-like manner.

JACOB LOUIS SNOEK. 

